Waveguide polarizer and a circularly polarized antenna

Abstract

A waveguide polarizer for converting between a linearly polarized electromagnetic field in a first waveguide and a circularly polarized electromagnetic field in a second waveguide is provided. The waveguide polarizer includes a structure interconnecting the first and second waveguide which includes a waveguide excitation arrangement with a bifilar helical shape. A circularly polarized antenna arranged to be connected to the first waveguide of the waveguide polarizer and a satellite arrangement are also provided.

What is claimed is: 
     
       1. A waveguide polarizer for converting between a linearly polarized electromagnetic field in a first waveguide and a circularly polarized electromagnetic field in a second waveguide, wherein the waveguide polarizer comprising:
 a structure interconnecting the first and second waveguide comprising a waveguide excitation arrangement with a bifilar helical shape, 
 wherein the structure comprises a transition waveguide interconnecting the first waveguide to a third waveguide, wherein the transition waveguide provides an impedance match between the first waveguide and the third waveguide. 
 
     
     
       2. The waveguide polarizer according to  claim 1 , wherein the waveguide excitation arrangement with the bifilar helical shape is galvanically connected to the first waveguide on opposing sides. 
     
     
       3. The waveguide polarizer according to  claim 2 , wherein the waveguide excitation arrangement with the bifilar helical shape is galvanically connected to ridges on opposing sides of the first waveguide. 
     
     
       4. The waveguide polarizer according to  claim 1 , wherein the first waveguide has a super-elliptical cross-section. 
     
     
       5. The waveguide polarizer according to  claim 1 , wherein the first waveguide has a rectangular cross-section. 
     
     
       6. The waveguide polarizer according to  claim 1 , wherein the first waveguide has a rectangular cross-section with rounded edges. 
     
     
       7. The waveguide polarizer according to  claim 1 , wherein the first waveguide has a cross-section including ridges. 
     
     
       8. The waveguide polarizer according to  claim 1 , wherein the second waveguide has a super-circular cross-section. 
     
     
       9. The waveguide polarizer according to  claim 1 , wherein the second waveguide has a circular cross-section. 
     
     
       10. The waveguide polarizer according to  claim 1 , wherein the second waveguide has a square cross-section. 
     
     
       11. The waveguide polarizer according to  claim 1 , wherein the second waveguide has a square cross-section with rounded edges. 
     
     
       12. The waveguide polarizer according to  claim 1 , wherein the transition waveguide has a length that is a quarter of the wavelength of the propagating electromagnetic field in the first waveguide. 
     
     
       13. A circularly polarized antenna arranged to be connected to a second waveguide of a waveguide polarizer for converting between a linearly polarized electromagnetic field in a first waveguide and the circularly polarized electromagnetic field in the second waveguide, wherein the waveguide polarizer comprising:
 a structure interconnecting the first and second waveguide comprising a wave-guide excitation arrangement with a bifilar helical shape, 
 wherein the structure comprises a transition waveguide interconnecting the first waveguide to a third waveguide, wherein the transition waveguide provides an impedance match between the first waveguide and the third waveguide. 
 
     
     
       14. The circularly polarized antenna according to  claim 13 , wherein the length of the second waveguide of the waveguide polarizer is such that evanescent modes generated by the waveguide excitation arrangement contribute significantly to the antenna radiation properties. 
     
     
       15. The circularly polarized antenna according to  claim 13 , wherein the length of the second waveguide of the waveguide polarizer is such that no evanescent modes generated by the waveguide excitation arrangement contribute significantly to the antenna radiation properties. 
     
     
       16. The circularly polarized antenna according to  claim 13 , further comprising one or more choke rings arranged around the second waveguide. 
     
     
       17. A satellite arrangement comprising a waveguide polarizer for converting between a linearly polarized electromagnetic field in a first waveguide and a circularly polarized electromagnetic field in a second waveguide, wherein the waveguide polarizer comprising:
 a structure interconnecting the first and second waveguide comprising a wave-guide excitation arrangement with a bifilar helical shape; 
 wherein the structure comprises a transition waveguide interconnecting the first waveguide to a third waveguide, wherein the transition waveguide provides an impedance match between the first waveguide and the third waveguide.